The present invention relates to a process for the production of artificial turf and to improved artificial turf. The process comprises tufting fibers into a primary backing to form a greige good, wherein the fibers are treated via corona discharge either before or after the tufting step, and applying a precoat to the back surface of the greige good wherein the precoat comprises a reactive polyurethane mixture. The artificial turfs of the present invention comprise a greige good having fibers tufted into a primary backing, and a precoat wherein the face surface of the precoat is adhered to the back surface of the greige good and the precoat comprises a polyurethane forming composition. The fibers tufted into the primary backing in this embodiment of the invention are treated via corona discharge either before the tufting step or after the tufting step.
Tufted goods, including carpeting and artificial turf, are manufactured by tufting yarns into a primary backing. The tufts are secured by applying at least one adhesive formulation to the primary backing side of the carpet/primary backing (“greige good”). Polyurethanes have largely replaced SBR latex as the backing material of choice for demanding outdoor applications such as athletic turf due to the inherent resistance of polyurethane against water degradation and generally superior durability. Nylon with its polar characteristics bonds quite well with precoats made with polyurethanes.
Recently, there has been a trend in the industry to move towards using polyolefin fibers or tape, such as polyethylene, because these materials are considerably less abrasive than nylon, and thus reduce the incidence of skin scraping injuries. These polyolefins are non-polar and thus bonding to polyurethane precoats is somewhat diminished resulting in lower tuftbinds compared to that of nylon turf.
Tufted carpet and a process for preparing the tufted carpet is described in U.S. Pat. No. 5,714,224. The tufted carpet of the '224 patent comprises a moisture barrier layer. More specifically, this carpet comprises a primary backing stitched with loops of yarn to form a tufted structure projecting outwardly from the primary backing, a layer of latex affixed to the primary backing, a layer of polyolefin affixed to the layer of latex, and a secondary backing comprising a woven polyolefin, which is affixed to the layer of polyolefin. The process described therein comprising providing a primary backing stitched with loops of yarn to form a tufted structure projecting outwardly from the primary backing, providing a secondary backing comprising a woven polyolefin, applying a layer of polyolefin onto the secondary backing, interposing a layer of latex between the primary backing and the polyolefin layer, and laminating the primary backing, the latex layer, the polyolefin layer, and secondary backing layer together.
Carpets having fluid barriers are described in U.S. Pat. No. 5,612,113. These carpets have a primary backing into which tufted yarn is stitched, a secondary backing to provide dimensional stability, and a thin film of a material which is impervious to spills, with the film being bonded to either the primary backing or the secondary backing by an adhesive which is provides an adequate bond and is insoluble to spilled fluids. Suitable materials for the thin film include polyethylene, polypropylene, polyurethane, polyester, polyvinylchloride (PVC), combinations thereof and similar thermoplastic materials which may be surface treated, as well as composite structures formed from laminates of these fibers with non-woven or woven fibers and either with or without reinforcing fibers. Corona treatment of the film on one side is broadly disclosed as possibly being sufficient to render the film bondable to the backing.
Copending U.S. application Ser. No. 10/028,897 filed on Dec. 18, 2001 describes tufted goods (including carpets and artificial turf) which can be made without a secondary backing. In general, secondary backings have been necessary in carpets and in processes for producing carpets to provide dimensional stability. As described therein, corona-treatment of a flexible film which is contacted or laminated to a polyurethane precoated greige good or to a foam layer applied to a precoated greige good creates a bond that is strong enough to render the resultant cured carpeting article dimensionally stable, with no secondary backing. The delamination strength of these cured tufted goods exceeds that of conventional tufted goods. It is possible to include secondary backings in the tufted goods, but this generally only results in further increases the costs of the processes and the resultant products, without further improvements in properties.
U.S. Pat. No. 3,962,386 describes corona discharge treatment of foam fibrillated webs. These foam fibrillated fibrous webs are prepared by an extrusion process. The foam fibrillated fibrous webs may be treated via corona-discharge to provide improved internal adhesion of the webs when they are laminated to form a non-woven fabric. These webs do not have tufts, greige goods or precoats as required by the present invention.
Nonwoven fabrics and a method of bonding the nonwoven fabrics are disclosed in U.S. Pat. No. 4,401,708. The web of fibers can be treated with microwave energy and a polar solvent (column 1, line 60 through column 2, line 4). Pretreatment of the fibers with corona discharge is also disclosed as improving the adhesion between the fibers of the nonwoven fabrics. Tufted goods are not disclosed by the '708 patent.
U.S. Pat. No. 5,221,394 discloses a method for manufacturing backed, pressure-adherent industrial carpeting. This carpeting comprises a backing film and an adhesive on one side of the backing film. The other side of the backing film is heat laminated to a web of carpeting to reinforce the carpeting and provide it with an adhesive. Corona discharge of the backing film is disclosed, and heat lamination is used to bond the fibers and the backing. This reference discloses improved bonding between the corona treated backing and the release layer.
Tufted products having improved backing are disclosed in U.S. Pat. No. 5,445,860. These tufted products are made by, for example, tufting pile yarn fibers into a tufting backing which is composed of a primary backing, a secondary backing and an elastomer sandwiched between the primary and secondary backings. It is also possible for the tufting backing to be composed of only a primary backing and an elastomer adhered to the primary backing. Thus, the secondary backing is optional. When a secondary backing is present, the elastomer is sandwiched between the primary and secondary backing layers. The elastomer may be applied as a solid sheet of elastomer, or it may be melted and applied. The solid sheet of elastomer is heated at some point to allow the elastomer to flow in and around the pile yarn fibers. Once the elastomer layer is cooled, the pile yarn fibers are bonded to the tufting backing. It is further disclosed that the bonding of the elastomer to the primary backing may be improved by treating the primary backing with a corona discharge or gas flame. Bonding between the primary backing and the elastomer may also be improved by suctioning the elastomer to the primary backing with, for example, a vacuum.
U.S. Pat. No. 6,171,678 discloses carpeting which exhibits improved tuft bind and/or improved elongation. These improvements are due to a particular polyol formulation used in the reactive polyurethane adhesive. Corona discharge is not discussed in U.S. Pat. No. 6,171,678.
Advantages of the present invention include artificial turf materials exhibiting improved properties. More specifically, these exhibit improved tuft bind between non-polar polyolefin turf materials and polyurethane precoats used to back the artificial turf.